This invention relates to a mass production technique of a semiconductor integrated circuit device, and more particularly, to a technique effectively applicable to a semiconductor production process, in which when a large number of wafers are continuously processed over a plurality of steps, the process is carried out in a mass production line wherein the lithographic step of wafers on which a film containing a transition metal such as ruthenium (Ru) is deposited and the lithographic step of wafers belonging to other steps are commonly used.
In the industrial fields other than that of the manufacture of a semiconductor, there is known a technique wherein a platinum group element is dissolved in a dissolution solution and isolated for the purpose of collecting the platinum group element from wastes or the like.
Japanese Laid-open Patent Publication No. Hei 7-157832 (Ito et al.) discloses a technique of recovering noble metals, such as gold, platinum group elements and the like, from used electronic parts, noble metal-containing, wasted catalysts, and a used jewelry by dissolution thereof in a dissolving solution For the dissolution of noble metals, there is used a dissolving solution which is obtained by mixing an aqueous solution of an inter-halogen compound (e.g. ClF, BrF, BrCl, ICl, ICl3, IBr or the like) and an aqueous solution of a halogenated oxoacid (iodic acid, bromic acid, chloric acid or the like) at a ratio in the range of 1:9 to 9:1. The noble metal dissolved in the solution is first separated as a halogenated complex, to which a solution of a compound (e.g. sodium hydroxide, sodium borohydride, hydrazine or its salt, sulfurous acid or its salt, a bisulfite or the like) is then added, thereby collecting the metal.
Japanese Laid-open Patent Application No. Hei 7-224333 (Wada et al) discloses a technique of dissolving out, in the form of an aqueous solution, an alloy formed by nuclear fission and containing noble metals, such as ruthenium (Ru), rhodium (Rh), palladium (Pd) without undergoing such a pretreatment as by liquid metal extraction by immersing the alloy in a dissolving solution of hydroiodic acid (or hydrobromic acid), to which an iodine simple element is added. It is stated that the dissolving solution has a concentration of hydroiodic acid (or hydrobromic acid) ranging from 5 to 57 wt %, and a concentration of the added iodine simple element ranging from 0.01 to 0.5 moles per liter of the former aqueous solution.